Example 10. Maria is retired and withdraws money from her retirement account. But a tax of 20% is automatically withheld. If she needs $1200, how much must she actually request?

Solution 1.. Since 20% will be withheld, Maria will receive 80% of her request. So the question is: $1200 is 80% of how much?

80 : 100 = 4 : 5 = 1200 : ?

4 has been multiplied by 300. Therefore, 5 must be multiplied by 300:

4 : 5 =1200 : 1500.

$1200 is 80% of $1500.

In other words, since 5 is one and a quarter times 4, then Maria must always request one quarter more than what she needs. One quarter of $1200 is $300. Therefore she must request $1200 + $300 = $1500.

It is then a simple matter to see that 20%, or a fifth, of $1500 is $300, so that her net amount will in fact be $1200.